Different styles and types of magazines are used with various types of firearms. Typically, all magazines include sidewalls that guide the cartridges as well as prevent the cartridges from falling out of the magazine. Some magazines such as box magazines and drum magazines have been made of plastic. However, other types of magazines, such as pan magazines that may be used in connection with Lewis machine guns, may also be made of plastic.
In recent years, plastic magazines have become popular for use with semiautomatic rifles, in part, because of their favorable price and high reliability. Prior to the rise in popularity of plastic magazines, sheet metal magazines were commonly used. However, as a result of an impact, sheet metal magazines have a tendency to dent, which may not be readily detectable to marksmen and, thus, the marksmen may not identify this defect. In contrast to sheet metal magazines, instead of denting from an impact, the elasticity of plastic enables most dents to pop out of plastic magazines and, thus, the plastic magazine is again in its substantially original form. Alternatively, plastic magazines may break from an impact, which makes the defect readily apparent to the marksmen.
In some example plastic magazines, such as described in EP 0 154 356 A2, an intermediate layer is injected into and/or added onto an upper part of sidewalls to strengthen the lip of the magazine and to ensure that the size of the lip corresponds to a slot of a receiver of the firearm. In other examples, such as described in U.S. Pat. No. 3,383,790, a piece of sheet metal forms a lip of a magazine by coupling the sheet metal to the top of the magazine's body.
Some difficulties were encountered when plastic magazines were initially experimented on for use with, for example, the 1947 Kalashnikov rifle, because sand or other derby would enter and jam the feed mechanism and the cartridges within the magazine. However, modern plastic magazines eliminate at least some of the problems encountered during these early experiments with plastic magazines. Modem plastic magazines are in fact as reliable as sheet metal magazines, but, in some instances, are firmer, lighter and more moldable.
Some firearms are configured to use 7.62×51 mm cartridges (e.g., a NATO round) that are each slightly tapered and, thus, the front edge of a stack of these cartridges is also tapered. Some magazines used with NATO rounds are curved. However, sheet metal magazines have straight sides because curved sheet metal magazines are significantly more expensive to produce and may pose issues associated with production defects. In contrast, curved plastic magazines may be produced for use with NATO rounds that are more reliable and less expensive to manufacture.
Some rifles such as, older rifles, were manufactured solely for use with sheet metal magazines. However, in recent years, attempts have been made to manufacture plastic magazines for use with these rifles. In developing plastic magazines, the dimensions of the corresponding sheet metal magazines have to be kept in mind. However, because of the material properties of plastic, the walls of plastic magazines are relatively thicker than the walls of sheet metal magazines. While the relatively thicker walls of plastic magazines do not effect a staggered zigzag arrangement of cartridges within the magazine, the relatively thicker walls do increase the plastic magazine's width. In particular, the plastic magazine's width is associated with the thickness of the walls and the necessary space between a tip of a cartridge and the front side of the magazine. The space between a tip of a cartridge and the front side of the magazine substantially prevents the cartridges from jamming. The size difference between plastic magazines and sheet metal magazines leads to incompatibilities between plastic magazines and rifles manufactured solely for use with sheet metal magazines.
One such rifle is the G3 rifle, which began production in the 1950's. As with all firearms manufactured during this era, the G3 rifle was manufactured for use with sheet metal magazines, as plastic magazines were not a feasible production option at the time. As such, the dimensions of the slot of the receiver of the G3 rifle corresponds to the dimensions of a sheet metal magazine and not the dimensions of a plastic magazine, even though both the sheet metal magazine and the plastic magazine are sized to hold the same size cartridge (e.g., NATO cartridges). While the G3 rifle began production decades ago, the G3 rifle, as with other such rifles, is still widely used throughout the world. Therefore, there is a demand by owners' (e.g., armies that use these rifles) of these rifles to update or replace components on their rifles such as, for example, replacing sheet metal magazines with more cost efficient and reliable plastic magazines. However, while there is a demand for replacement plastic magazines, plastic magazines are thicker and the dimensions of the magazine receiver in the weapon does not change, so there is less room in the magazine for conventional NATO rounds. While known plastic magazines may be configured to hold smaller rounds, which would enable the size of known plastic magazines to be compatible with a G3 rifle, it is extremely unlikely that an army affiliated with NATO supplies would agree to use cartridges that are, for example, a half millimeter shorter than a NATO round (e.g., not a NATO round).